Process of and apparatus for tanning hides or skins



Patented May l6, I899.

P. e. sALoM. PROCESS OF AND APPARATUS FOR TANNING HIDES 0B SKINS.

A nmso filed Apr. s, 1598.

(No Model.)

UNITED I STATES PATE T OFFICE.

PEDRO e. SALOM, or PHILADELPHIA, PENNSYLVANIA.

PROCESS OF AND APPARATUS FOR TANNING HIDES OR SKINS..

SPECIFICATION'fOrming part Of Letters Patent No. 625,204, dated May 16, 1899.

Application filed April 8, 1898. Serial No. 676,968- illo model.)

To all whom, it may concern:

Be it known that I, PEDRO G. SALOM, a citi zen of the United States, residing in Philadelphia, Pennsyh'ania, haveinven ted a Process of and Apparatus for Tanning Hides or Skins, of which the following is a specification.

My invention relates to certain improvements in the process of and apparatus for the treatment of skins and hides for the purpose of making leather in connection with what is termed mineral or chrome tanning, for which application for patent was filed on the 21st day of October, 1897, by Samuel P. Sadtler, Serial No. 655,929.

It is known that if hides or skins are impregnated with a chromate, such as bichromate of potash, and an acid, such as hydrochloric or sulfuric acid, and then submitted to the action of a reducing agent sufficiently rapid in its action chromic oxid is separated out through the body of the skins and an insoluble leather possessing numerous excellent qualities is obtained.

In the application mentioned above the reducing agent is nascent hydrogen electrolytically produced, such agent elfecting the reduction to chromium sesquioxid of the chromic acid with which the skin is impregnated. Electrolytically-produced nascent hydrogen can be made to act upon the chromic acid in site, so that an immediate combination of the hide fiber and the liberated chromium sesquioxid takes place. The result is a chrometanned leather with all the characteristic qualities of insolubility in water, freedom from shrinkage, softness, and pliability recognized as belonging to this class of products. There are no side products to be washed out of the tanned skins, the sole product of the reaction besides the chromium sesquioxid being water.

In carrying out the above process great care must be exercised in adjusting the conducting-plates and the skins, so that the nascent hydrogen which is electrolytically produced will act immediately upon all portions of the skins. Consequently the plates had to be spaced and great care exercised in arranging the skins and plates. By my invention, however, I can clamp the skins between the plates without exercising the care necessary heretoing porous allows the free circulation of the liquor in the cell or tank B. I have shown the plates arranged one above another and connected to a terminal strip 1), and this terminal strip is connected to the negative pole of a dynamo O or other source of electric supply.

In this way the spongy-lead plates A constitu te the negative electrode of a galvanic couple. The skins having been properly prepared by immersion in abath containing bichromate of potash and sulfuric acid are placed between the spongy-lead plates A, as indicated in the drawings, w being the skins, the plates preferably beingin contact with the skins, so as to clamp them evenly, insuring a perfect contact. The impregnated skins having been placed between the metallic plates constituting the negative electrodes, the whole is then immersed in a bath, which is by preference similar to the one by which the skins are impregnated, and maybe a solution in water of three per cent. sulfuric acid and five per cent. of bichromate of potash. This constitutes a very effective electrolytic bath for the purpose, as it prevents any washing out of hichromate from the impregnated skin.

The impregnation of the skins or hides may, if desired, be efiected by the same bath which constitutes the electrolyte, although it is preferable to impregnate the skins before introdueing them into the electrolytic bath.

The positive electrode e may be made of any suitable conducting substance, such as a sheet of lead or conducting carbon, and may be placed, as shown, within the tan k, care be ing taken to prevent contact with the spongylead plates.

The terminal of the electrode is connected to the positive pole of the dynamo or other source of electrical supply, as shown.

closing the circuit hydrogen isliberated from all the surface constituting the negative electrode, and the reaction which takes place may be described as follows: Bichromate of potash (K Or O is broken up into the sesquioxid of chromium, (Or o H-O plus potassium oxid, (K O,) which latter in the presence of sulfuric acid becomes sulfate of potash, (K 80 Bichromate is broken up into sesquioxid of chromium plus sulfate of pot ash. It is therefore these three atoms of oxygen with which the nascent hydrogen liberated at the negative electrode combines to form water, and thereby indirectly reduces the chromic acid in the bichromate to sesquioxid of chromium, which remains in the skin and converts it into leather.

The process may be carried out by the use of other salts than a chromium salt such, for instance, as salts of iron or aluminium.

As an example of a specific mode of carrying out my process I may say that in practice I have taken goatskins and cut them upinto pieces about six and one-half inches square. Three of these pieces I piled with a pair of lead plates,one piece being between the plates and one on the outside of each plate, the whole pile being completed by the application of two plates connected together and outside of the pieces of skin. This pile is then placed in a bath of bichromate of potash after the skins have been steeped therein, the plates between the pieces of skins and connected to the negative electrode of a source of current, the outer plates being connected to the positive electrode. A current of five amperes and four volts pressure was passed through the solution forfive hours, at the end of which time the skins were found to be practically tanned. It should be observed that when whole goatskins are tanned correspondingly larger plates must be used, and the quantity of current necessary will be materially reduced, as the internal resistance will decrease with the increased size of the plates.

I claim as my invention 1. The process of tawing or tanning hides or skins, said process consisting in impregmating the hides or skins with a chromate and an acid. and mounting the skins in contact with negative plates of spongy lead in an electrolytic bath, substantially as described.

2. The within-described process of tawing or tanning hides or skins, said process consisting in impregnating the hides or skins with a chromate and an acid and mounting the skins between the spongy-lead plates forming the negative poles of an electrolytic bath, substantially as described;

3. The within-described process of tawing or tanning hides or skins, said process consisting in impregnating the hides or skins with a chromate and an acid and clamping the skins between plates of spongy lead form'- ing the negative pole of an electrolytic bath, substantially as described.

4. In an apparatus for electrolytically tanning or tawing hides'or skins, said apparatus consisting of a tank, a series of grids of conducting metal having spongy lead mounted thereon andfforming the negative pole of a galvanic couple and arranged to receive between them the skins to be tanned or tawed by reducing action of nascent hydrogen electrolytically produced, substantially as described.

In testimony whereof I have signed my- PEDRO G. SALOM.

Witnesses:

CHAS. H. BANNARD, MURRAY 0. BOYLE. 

